Caves of Folx-les-Caves

The Caves of Folx-les-Caves rank among the most unusual underground sites in the Walloon Brabant province of Belgium. Beneath the small village of Folx-les-Caves, part of the municipality of Orp-Jauche, lies a network of man-made galleries spreading across roughly six hectares. Despite the name, these are not caves in the geological sense — they are the remains of an old quarry, hand-carved into soft limestone rock.

How did the underground galleries form?

The site owes its existence to the extraction of tuff, a soft, easily worked limestone rich in calcium carbonate. The stone was mainly quarried for agricultural use: once ground down, it served as a lime fertilizer spread on the surrounding fields. The exact period when digging began remains uncertain. Some local traditions trace the galleries back to prehistoric times, but it is considered more likely that quarrying started sometime between the late Roman era and the early Middle Ages. What is documented with certainty is that the caves already existed before 1606, the earliest confirmed reference to the site.

What roles have the caves played through the centuries?

Above all, the history of the caves is a history of shelter. Local residents repeatedly took refuge underground during periods of conflict that swept through the region, all the way through the Second World War, when the tunnels offered protection during the German occupation. The sprawling network of passages also served as a hideout for people living outside the law — most notably the gang led by Pierre Colon and his wife Marie Tirion, who hid in the galleries before eventually being captured and hanged.

In peacetime, the caves took on far more practical functions. The steady, cool temperature found some fifteen meters below ground made the space useful for storing farm machinery, and for many years part of the galleries were even used to cultivate mushrooms, whose growth thrives in exactly this kind of stable, dark, humid environment.

Can visitors explore the Caves of Folx-les-Caves today?

Access to the underground network is via a narrow, steep staircase descending roughly fifteen meters below the surface. Given the scale and irregular layout of the galleries, the site calls for caution, and since being listed as a protected heritage site in 1993 it has remained privately owned, with no general public access.

The only legal way to see the caves is through organized school visits, arranged in partnership with the Walloon Brabant Museum of Archaeological Interpretation (MiaBw), based in Hélécine. This institution is responsible for documenting the site's history and introducing it to younger visitors.

Frequently asked questions

Are the Caves of Folx-les-Caves natural caves? No. They are the result of hand quarrying of limestone tuff, not natural geological formation.

How large is the underground network? The galleries extend across an estimated six hectares beneath the surface.

Can the caves be visited independently? No — the site is privately owned, and access is limited to school trips organized through the MiaBw museum in Hélécine.

What were the caves used for historically? They served as wartime shelter, a hideout for criminal gangs, storage space for farm machinery, and a site for growing mushrooms.